There are a great number of free password generating software and password management services, such as lastpass.com, keepass.info, etc. We usually generate a random password and store it in an encrypted database, however, if your master password is stolen, all of your passwords will be revealed.
Dual Password Generator is a free, lightweight, portable Windows application which could create a strong password based on a seed – your old password, it contains a pool of 8836( 94 x 94 ) random characters, as seen below:
Once you entered an old password, the app will look up the pool to generate the new password, if the old password is “123456″, it will find the intersection of column M and row N, where M = 18, N = 17. The decimal number of the first character( ’1′ ) is 49, while the base number is 33( ‘!’ ), so the row number of ’1′ is 49-33+1 = 17, the column number of ’1′ is determined by the index number of the second character( ’2′ ), which is 50 -33 + 1 = 18, so the first character of your new password is ‘_’, the second character is ‘s’, as seen below:
The theory is similar to Tabula Recta. If someone hacked your original password of a certain account( for example, Paypal, FaceBook, Twitter, Amazon, etc. ) but your actual password is generated with Dual Password Generator and your original password, he can do nothing to your account. On the contrary, if the data file of your Dual Password Generator is revealed but the thief does not know your original password, the result is same.
It’s recommended that you save your passwords with your favorite password manager, and then generate the actual password on the fly with Dual Password Generator and your ‘seed’ – the old password.
You can create a new file which contain the pool of random characters, however, please keep in mind that if the pool is changed, the output password will also change.
Dual Password Generator works on Windows 7 and Windows XP, download it now( 846KB ).